Since so many consumers hop from smartphone to desktop to tablet and back again multiple times a day, Web publishers have rushed to embrace responsive design: a technology that automatically resizes content to fit any screen.
The responsive movement has been a win for users, who increasingly want to consume content on multiple devices. It also has yielded a welcome by-product: better mobile advertising opportunities. Inherently, responsive sites place mobile ads front and center, rather than relegating them to the sidelines.